Arrangement in breathing apparatus



P 1964 K. w. SVENSON 3,149,631

ARRANGEMENT IN BREATHING APPARATUS Filed Jan. 17. 1961 filial-Ell; I; I

SU8-PRESSURE INVENTOR AIVW" m arm/v,

ATTORNEYS United States Patent ARRANGEMENT 1N BREA'HHNG APPARATUS KnutWilhelm Svenson, Lidingo, Sweden, assignor to Svenska AlrtiebolagetGasaccumulator, Lidingo, Sweden, a corporation of Sweden Filed .ian. 17,19631, Ser. Ne. 83,278 Claims priority, application Sweden Feb. 18, 19603 Claims. (Cl. 128-142) The present invention relates to a breathingapparatus which is suitable for use under water or in an unbreathableatmosphere, such as smoke-infested air. In breath- 7 ing apparatus ofthis kind there is a general requirement of easy breathability. That isto say, the sub-pressure that has to be created by the wearer of theapparatus when breathing in should be low and the overpressure that hasto be produced in a similar manner in breathing out should also be low.If a breathing apparatus does not meet these requirements, there willresult an unnecessarily large amount of work for the mere breathingprocess, so that the useful work that can be performed by the wearer iscorrespondingly reduced.

In a breathing apparatus which is to be used under water down to depthsof the order of 50 or 60 meters there is the further requirement thatthe sub-pressure which is necessary for breathing in should stay withinreasonable limits, even at the large air quantities that have to besupplied at such depths. Obviously, the apparatus must also beconstructed so as to be able to de iver such quantities.

In breathing apparatus for use in an unbreathable atmosphere, such assmoke-infested an, the same requirement for delivering very largequantities of air is not present, but on the other hand it is verydesirable to keep the breathing resistancies at low values so thatbreathing through the apparatus will not be inconvenience and tiresome.

It has generally been held, that in breathing apparatus of good qualitywhich meets the above requirements, the sub-pressure required forinhaling may be of the order of 10 mm. water column, whereas the overpressure required for exhaling may have reached a value of a few mm.water column.

In earlier forms of breathing apparatus having a membrane which ismovable in response to the difference in pressure between thesurrounding medium and the breathing passages of the wearer to controlthe inhalation valve, it was necessary, in order to meet theserequirements, to provide a membrane of a relatively large area to obtainthe necessary force for con-trolling the inhalation valve. This in turnlead to comparatively large dimensions of the valve unit comprising theinhalation valveand the exhalation valve, as well as the membrane andother details, so that a unit of this type could hardly be used incombination with a mouth piece.

Furthermore, various constructions of breathing apparatus have beenproposed having a substantially smaller membrane for controlling theinhalation valve. In this way the dimensions of the valve unit could bemade small enough to make it usable in connection with a mouth piece.However, these known apparatus types did not work satisfactorily, sincethe sub-pressure required in inhalation was excessively large, of theorder of 40' to 50 mm. water column, and further, these types wereunable to supply the large air quantities required at the larger depthsof the order of ten meters or more.

On the accompanying drawing, FIG. 1 shows an embodiment of the presentinvention and FIG. 2 shows some curves representing for variousbreathing apparatus types the sub-pressure required in inhalation forthe supply of a certain air quantity per unit of time.

The curve A of FIG. 2 illustrates in principle the relationship betweensub-pressure and supplied air quantity in liters per minute which isvalid for the earlier types of breathing apparatus. As is apparent fromthe curve, a certain relatively low sub-pressure is required to open theinhalation valve and let in the air for breathing. The requiredsub-pressure then increases relatively slowly with an increase in theair quantity supplied. For larger quantities of air, however, therequired sub-pressure iricreases rapidly and there is a limit to the airquantity supplied per unit of time, the apparatus being unable todeliver quantities in excess of this value in spite of a very largeincrease in the sub-pressure.

As was mentioned above, the curve A is representative of earlier typesof breathing apparatus. It should be noted, however, that the initialvalue at which the inhalation valve normally opens is different fordifferent types, as is the maximum air quantity delivered per unit oftime.

It is apparent from the introductory discussion of the requirements onbreathing apparatus that an apparatus according to curve A is notentirely convenient, primarily in view of the large sub-pressure that isrequired for the apparatus to deliver suificient quantities of air.

The application of the present invention results in a breathingapparatus which is able to deliver very large air quantities per unit oftime without any appreciable increase in the sub-pressure that isrequired. Further, the apparatus can be arranged to have the inhalationvalve open already at a very low inhalation sub pressure in spite of thefact that the membrane actuating the valve has a small area. Owing tothese favorable characteristics, the apparatus can be used withadvantage under water down to very large depths as well as for work in anonbreathable atmosphere.

The invention is predicated on a valve unit comprising an inhalationvalve, a membrane for actuating the same, and an exhalation valve andcontaining a wall separting space containing the inhalation valve from aspace bordered by the membrane. Valve units of such construction arepreviously known but the partition provided in the valve unit was thendifferently located and served another purpose than according to thepresent invention.

According to the invention, the said partition is arranged so as to makethe breathing gas flowing in from the inhalation valve create aninjector efiect tending to set up a sub-pressure in the space borderedby the membrane, a predetermined degree of compensation of the saidefiect being provided simultaneously through a direct connectionarranged between the space containing the inhalat-ion valve and thespace bordered by the membrane, through which connection a limited gasflow is possible into the space bordered by the membrane. The saidconnection may preferably consist of a hole provided in the partitionbetween the two spaces and should be dimensioned in such a way that thesub-pressure required for opening the inhalation valve is substantiallyconstant in- 3 dependently of the gas quantity per unit of time thatenters through the inhalation valve.

The invention will be described in more detail with reference to theaccompanying drawing, in which FIG. 1 shows an embodiment of theinvention.

In the embodiment described, the apparatus is provided with amouth-piece 1, but the invention may also be applied to a breathingapparatus of the face mask type. The mouth-piece 1 is provided with atube 2 of elastic material, such as rubber, into which the valve unit 3is inserted. Breathing gas is supplied from a tube, not shown in thedrawing, which is connected with a connecting stud 4 at the end of thevalve unit 3. An inhalation valve 5 is provided in an insert 6 of theunit and is controlled via a valve stem 7 and a crank lever 8 by amembrane 9 mounted in a membrane housing 11 The housing has a perforatedcover 11 allowing the surrounding medium to act on the outside of themembrane 9. Preferably, an exhalation valve 12. is placed on themembrane 9. Finally, a hole 13 is provided in the partition of the unit3 to allow passage of inhaled or exhaled air.

The details of the breathing apparatus so far described are of known andconventional construction. However, a known apparatus of this type isvery unsatisfactory in operation in that a very large sub-pressure isrequired to open the inhalation valve and also for the reason that theapparatus can supply only an insignificant amount of air per unit oftime even for a very large'increase in the inhalation sub-pressure. Theoperating characteristic of such known apparatus is therefore largely ofthe type illustrated by curve B of FIG. 2, from which is apparent,firstly, that the inhalation valve opens only at a relatively largesubpressure and, secondly, that the apparatus is able to supply only asmall amount of air per unit time. The investigations on which thepresent invention is based have shown that the latter feature is largelydue to the fact that the air entering through the inhalation valve isblown towards the inside of the membrane, thereby preventing it frommoving inwardly to the extent that is required in response to a largerinhalation sub-pressure. A known apparatus of such construction istherefore not suitable for use at large depths under water or in anonbreathable atmosphere.

As is'apparent from the drawing, there is provided in the valve unit 3 apartition 14, which separates a space 15 of the valve unit containingthe inhalation valve from a space 16, which is bordered by the membrane9. The partition 14, according to the invention, is located andconstructed so as to deviate the gas entering through the inhalationvalve 5 towards the mouth-piece 1, thereby preventing the gas fromexerting a pressure on the inside of the membrane 9. There is createdinstead through the injector elfect caused by the gas flowing from thespace 15 to the mouth-piece 1 a certain sub-pressure in the space 16,which would increase with an increase in the amount of gas supplied,unless steps are taken to counteract this effect. The operation of abreathing apparatus of this construction would be in accordance with thecurve C of FIG. 2. It is characteristic for the curve C that therequired sub-pressure is at first substantially constant for an increasein air quantity but decreases when the quantity of air supplied per unitof time exceeds a predetermined value, which is designated v on thedrawing. Such an operation does render the apparatus easily breathablebut it is nevertheless not desirable, since the inhalation of largequantities may create the impression of air being blown into the lungs.It is therefore desirable that the sub-pressure required at larger airquantities should not diminish but remain substantially constant.However, a small increase in sub-pressure may be of value, since such arelationship resembles more closely the physical conditions in ordinarybreathing.

It is apparent from this discussion that the operation of a breathingapparatus should be in accordance with curve D of FIG. 2, which meansthat the sub-pressure required for opening the inhalation valve shouldbe low and that with an increase in the gas supply the re quiredsub-pressure is substantially constant or rises slowly. This type ofoperation is obtained according to the invention by the provision of adirect connection be tween the space 15 containing the inhalation valveand the space 16 bordered by the membrane. This connection enables alimited flow of gas to the last mentioned space. In the embodiment shownin the drawing, this connection is in the form of a hole 17 of suitabledimensions, which is provided in the partition 14. In a breathingapparatus of such construction the gas entering through the inhalationvalve 5 will then be directed chiefly towards the mouth-piece 1 and thusbe supplied directly to the wearer. This air flow has an injector efiecttending to create a sub-pressure in the space 16. This effect iscompensated for to a desired extent by the air passing directly throughthe hole 17 into the space 16, the result being that the operation ofthe apparatus is in accordance with the preferable type of curve D.

The pressure of the breathing gas supplied through the connecting stud4- is normally of the order of 5 kg./cm. above that of the ambientmedium, whereas the pressure in the spaces 15 and 16 and in themouthpiece 1 should be approximately the same as that of the ambientmedium. For the purpose of providing a small actuating pressure for theopening of the inhalation valve 5, which means that only a small forcehas to be exerted by the membrane 9, the inhalation valve 5 is acted onby a spring 18 which is inserted under pressure between a flangedportion 19 provided on the valve stem 7 and the partition 14. The springis of such dimensions that the diiierence between the closing pressureexerted on the inhalation valve 5 and the force of the spring tending tounseat the inhalation valve 5 results in the desired small pressure foropening the inhalation valve. The spring 18 should furthermore have arelatively small active interval, so that its influence on the valvestem 7 ceases as soon as the inhalation valve 5 has opened.

The construction of the breathing apparatus in accordance with theembodiment shown on the drawing causes .the air entering through theinhalation valve 5 to be subjected to several changes in directionbefore it reaches the mouth-piece 1. The air first enters the spacesurrounding the valve stem 7, where it is deflected to the space 15.There are then two changes of direction before the air reaches themouth-piece 1. This has the advantage that the inhalation air does notreach the wearer in the form of a concentrated stream, which might bedisagreeable.

What is claimed is:

1. In a breathing apparatus, the combination comprising: a cylindricalcasing defining a valve chamber and including an opening at one endthereof for operatively communicating the chamber with a source ofbreathable air to permit flow of the air into the chamber; a movableflexible diaphragm mounted at and closing the other end of the casingand having one side thereof subjected to the ambient medium andresponsive to the difference between the pressure of the ambient mediumand the pressure within the chamber; an inhalation valve cooperatingwith said opening to control the flow of air into the chamber; means forcontrolling the inhalation valve in response to movement of themembrane; a partition within the casing disposed laterally of the casingaxis and having a diameter equal to the inner diameter of the casing,the partition dividing the casing valve chamber into a first spaceincluding the said opening and a second space including the membrane; anexhalation valve in the second space operatively communicating with theambient medium; a tube permitting passage of inhaled air to and exhaledair from a wearer; a communication port connecting the chamber with thetube, the partition being situated at the communication port anddividing the port into a first opening communicating with the said firstspace and a second opening communicating with the second space, thepartition forming with the first opening an injector means causing asub-pressure in the second space upon passage of inhaled air through thefirst opening, and the partition further defining a hole enabling alimited flow of air directly from the first space to the second space tocounteract the decrease in pressure in the second space caused by theinjected means.

2. The combination according to claim 1 wherein a portion of the meansfor controlling the inhalation Valve passes through the said partition.

3. The combination according to claim 1 wherein the inhalation valve ismounted outside the casing and is held against the opening by thepressure of the breathable air source, and the means for controlling theinhalation valve includes a lever Within the casing and operable to movethe inhalation valve away from the opening and permit flow of air oninward deflection of the flexible membrane.

References Cited in the file of this patent UNITED STATES PATENTS 102,269,500 Wildhack Jan. 13, 1942 2,886,033 Gagnan et a1 May 12, 19592,948,292 Fitt Aug. 9, 1960

1. IN A BREATHING APPARATUS, THE COMBINATION COMPRISING: A CYLINDRICALCASING DEFINING A VALVE CHAMBER AND INCLUDING AN OPENING AT ONE ENDTHEREOF FOR OPERATIVELY COMMUNICATING THE CHAMBER WITH A SOURCE OFBREATHABLE AIR TO PERMIT FLOW OF THE AIR INTO THE CHAMBER; A MOVABLEFLEXIBLE DIAPHRAGM MOUNTED AT AND CLOSING THE OTHER END OF THE CASINGAND HAVING ONE SIDE THEREOF SUBJECTED TO THE AMBIENT MEDIUM ANDRESPONSIVE TO THE DIFFERENCE BETWEEN THE PRESSURE OF THE AMBIENT MEDIUMAND THE PRESSURE WITHIN THE CHAMBER; AN INHALATION VALVE COOPERATINGWITH SAID OPENING TO CONTROL THE FLOW OF AIR INTO THE CHAMBER; MEANS FORCONTROLLING THE INHALATION VALVE IN RESPONSE TO MOVEMENT OF THEMEMBRANE; A PARTITION WITHIN THE CASING DISPOSED LATERALLY OF THE CASINGAXIS AND HAVING A DIAMETER EQUAL TO THE INNER DIAMETER OF THE CASING,THE PARTITION DIVIDING THE CASING VALVE CHAMBER INTO A FIRST SPACEINCLUDING THE SAID OPENING AND A SECOND SPACE INCLUDING THE MEMBRANE; ANEXHALATION VALVE IN THE SECOND SPACE OPERATIVELY COMMUNICATING WITH THEAMBIENT MEDIUM; A TUBE PERMITTING PASSAGE OF INHALED AIR TO AND EXHALEDAIR FROM A WEARER; A COMMUNICATION PORT CONNECTING THE CHAMBER WITH THETUBE, THE PARTITION BEING SITUATED AT THE COMMUNICATION PORT ANDDIVIDING THE PORT INTO A FIRST OPENING COMMUNICATING WITH THE SAID FIRSTSPACE AND A SECOND OPENING COMMUNICATIONG WITH THE SECOND SPACE, THEPARTITION FORMING WITH THE FIRST OPENING AN INJECTOR MEANS CAUSING ASUB-PRESSURE IN THE SECOND SPACE UPON PASSAGE OF INHALED AIR THROUGH THEFIRST OPENING, AND THE PARTITION FURTHER DEFINING A HOLE ENABLING ALIMITED FLOW OF AIR DIRECTLY FROM THE FIRST SPACE TO THE SECOND SPACE TOCOUNTERACT THE DECREASE IN PRESSURE IN THE SECOND SPACE CAUSED BY THEINJECTED MEANS.